This invention relates to processes for converting alkali metal sulfate values, especially sodium or potassium sulfate, into alkali metal hydroxide and alkali metal sulfate/sulfuric acid by electrodialytic water splitting.
Electrodialytic water splitting of aqueous neutral salts, in two-compartment cells, to form the corresponding acid and base is disclosed in C.A., Vol. 53, 11070b (1959) (Oda et al.). Additionally electrodialytic water splitting processes, in two-compartment bioplar membrane cells, to convert waste sulfate containing streams are disclosed in U.S. Pat. Nos. 4,082,835 and 4,107,015 (Chlanda et al.)
Rayon preparation is a well-developed technology which employs alkali metal sulfates in the preparation process. See for example, R. L. Mitch et al. "Rayon" in Encyclopedia of Polymer Science and Technology, Vol. 79, Intersciences Publishers (Div. of J. Wiley) 1969, pp. 810-847. Regeneration of alkali metal sulfate values, especially as Na.sub.2 SO.sub.4 /H.sub.2 SO.sub.4, or K.sub.2 SO.sub.4 /H.sub.2 SO.sub.4, from spent rayon spin baths is an energy intensive process requiring purification steps and make-up sulfuric acid. Due to increasing energy costs, an improvement in the efficiency of processes for regenerating of alkali metal sulfate values derived from rayon spin baths would be beneficial.
Accordingly, it is an object of the present invention to provide electrodialytic water splitting processes for converting aqueous alkali metal sulfate values contained in or obtained from rayon spin bath liquors into alkali metal hydroxide and alkali metal sulfate/sulfuric acid.
Other objects and advantages of the present invention will become apparent from the description which follows.